Water is the material of choice to extinguish most fires or to prevent combustible objects from burning. Water predominantly is supplied from a network of pipes or, in the case of a forest fire, for example, from natural waters. In fire fighting, water contacts burning objects which results in sufficient cooling such that the burning objects fall below their combustion or ignition temperature, and new ignition is precluded. In addition, when water contacts hot objects, the water vaporizes to produce steam, which expands and expels the air necessary for combustion.
When a fire is extinguished by spraying water on the fire, less than 10% of the sprayed water is effective because of water loss, such as by run-off or evaporation. This is particularly disadvantageous in the case of forest fires and wildfires because a considerable portion of the water often is transported a long distance at a great expense, and then is wasted. To date, it has not been possible to make optimum use of water in forest fires and wildfires because such fires are frequently preceded by a period of drought and, accordingly, the ground has a particularly high water absorptive capacity. The waste of water is a very important aspect of forest fire fighting because a forest fire typically consumes the dry undergrowth (e.g., grass, foliage, and heather) and leads to individual crown fires which then unite.
The problem of ineffective water usage also is encountered in other types of fires, for example, when a roof of a building is on fire. In this case, the water often reaches the lower stories of the building through floors, openings, and staircases, for example, and is thereby lost for fire fighting purposes. This creates a potential lack of water, such that the fire spreads from the burning roof downwards. In addition, the water running off to lower stories frequently results in considerable water damage.
Forest fires and brush fires annually cause the loss of millions of dollars worth of timber and other property. Extensive damage often occurs because by the time the fire is detected, and before control measures can be applied, the fire is out of control in a condition known as a “wildfire”. The direct property loss due to such fires is catastrophic, and the associated soil erosion and watershed problems also are significant. It is important, therefore, to minimize and control the spread of forest fires whenever possible.
Another problem encountered in fighting a forest fire is an inability to precisely determine which objects, or areas, have been sprayed and which have not. This is an especially difficult problem encountered in the aerial firefighting of forest fires. Effective fire fighting requires that all objects or areas of interest are sprayed, while minimizing double spraying of some objects or areas.
In order to improve the action of water when fighting a forest fire, thickened water or water containing a chemical fire retardant has been applied to timber and other foliage in the path of a fire to retard advancement of the flame front. Various methods of distributing the water, including direct spraying and aerial dropping, have been employed. Aerial dropping is advantageous because areas that are not easily accessible can be sprayed.
There are two types of fire retardants commonly employed in fighting forest, range, grass, and brushland wildfires. These fire retardants are classified as “short-term” or “long-term” retardants. Short-term retardants rely primarily upon water to retard combustion. Long-term retardants contain, in addition to water, a water-soluble chemical that effectively retards combustion for brief periods even after the water has evaporated.
The present invention is directed to compositions and methods of preventing, retarding, suppressing, and extinguishing fires by applying a sufficient amount of an aqueous composition containing an SAP, a colorant, and an opacifying agent to combustible objects, either before or after initiation of combustion.
Prior patents have disclosed the use of an SAP in the control of fires, for example, U.S. Pat. Nos. 5,190,110 and 5,849,210. U.S. Pat. No. 3,354,084 discloses a composition containing (a) an SAP, (b) a nonionic, water-insoluble solid, and (c) an optional nonionic or anionic water-soluble dye. The water-insoluble solid increases the viscosity of an SAP hydrogel for improved firefighting. It is essential that an aqueous dispersion of the insoluble solid has a resistivity of at least about 50,000 ohms, or the gel capacity of the SAP is diminished. The insoluble solids disclosed in U.S. Pat. No. 3,354,084 are essentially totally water insoluble and include titanium dioxide, silica gel, powdered aluminum, and calcium silicate, for example. The sole optional dye disclosed in U.S. Pat. No. 3,354,084 is rhodamine B.
European Patent Application 0 649 669 A1 discloses a fire extinguishing medium containing (a) an SAP, (b) a substance having a large surface structure, a capillary structure, or a fibrous structure, and (c) an optional biodegradable dye. The substances of component (b) are water-insoluble materials, like sawdust, cellulose, kieselguhr, ground plastics, ground foamed plastics, and hydrophobic silicon dioxide. This European application fails to disclose any specific dyes.